This invention relates to tufting machines and more particularly to a controlled needle tufting machine for performing overtufting operations.
Controlled needle tufting machines are known which operate to skip stitch in accordance with a program for forming tufted designs in a backing fabric. Basically these machines render selective needles or groups of needles inoperative while the remainder of the needles are operative to pierce the backing fabric upon each stroke of the needle bar. Examples of this type of machine are illustrated in U.S. Pat. Nos. 3,115,856; 3,259,088 and 3,881,432.
Overtufting is a process wherein a previously formed with pile fabric is then tufted to insert additional pile, such additional pile being stitched at predetermined locations in the base material and primary or base pile. Overtufting with yarn of different colors than the primary pile provides desirable and appealing patterning effects in the fabric, especially carpeting.
In the production of carpeting in this manner the base material with the primary pile is fed across the needle plate of the tufting machine with the primary pile disposed on the needle plate fingers and projecting downwardly toward the loopers or hooks which cooperate with the needles carrying the overtuft or secondary yarn. In the prior art the needle plate fingers are at substantially the same level as the top of the needle plate at the location where the fingers project from the needle plate. The backing material within which the primary pile is stitched is thus spaced above the needle plate fingers by an amount substantially equal to the height of the primary pile so that the height of the secondary pile formed about the loopers or hooks is more or less substantially equal to the height of the primary pile plus the distance that the loop seizing edge of the loopers or hooks are below the top of the needle plate fingers. The secondary pile, which of course is also stitched into the backing material, is therefore of a height substantially greater than the primary pile height. Because of this, a substantial amount of secondary pile yarn must be tip sheared after tufting so that the secondary pile and the primary pile will be level. The amount of yarn which is thus sheared is of course wasted. Thus, it is highly desirable to minimize the amount of yarn which must be sheared and thereby reduce the cost of the process.